Alternative Names

How the Test is Performed

, , and/or are measured before and after one or more of the following:

Water loading -- drinking large amounts of water or receiving fluids through a vein

Water deprivation -- not drinking fluids for a certain amount of time

ADH administration -- receiving antidiuretic hormone (ADH), which should cause the urine to become concentrated

After you provide a urine sample, it is tested right away. For urine specific gravity, the health care provider uses a dipstick made with a color-sensitive pad. The color the dipstick changes to tells the provider the specific gravity of your urine. The dipstick test gives only a rough result. For a more accurate specific gravity result or measurement of urine electrolytes or osmolality, your health care provider will send your urine sample to a lab.

How to Prepare for the Test

Eat a normal, balanced diet for several days before the test. Your health care provider will give you instructions for water loading or water deprivation.

Your health care provider will ask you to temporarily stop any medicines that may affect the test results. Be sure to tell your provider about all the medicines you take, including dextran and sucrose. Do not stop taking any medicine before talking to your doctor.

Also tell your provider if you recently received intravenous dye (contrast medium) for an x-ray. The dye can also affect test results.

Version Info

Last reviewed on 8/25/2013

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.

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